Porous body, additive manufacturing method for the body and apparatus for supporting and/or bearing a person

ABSTRACT

It is a feature of a porous body ( 10, 20 ) comprising a three-dimensional network of node points ( 200 ) joined to one another by struts ( 100 ), and a void volume ( 300 ) present between the struts ( 100 ), that the struts ( 100 ) have an average length of ≥200 to ≤50 mm, the struts ( 100 ) have an average thickness of ≥100 μm to ≤5 mm, and that the porous body has a compression hardness (40% compression, DIN EN ISO 3386-1: 2010-09) in at least one spatial direction of ≥10 to ≤100 kPa. The porous body according to the invention combines the advantages of a conventional mattress or cushion with ventilatability which results from its porous structure and is not achievable in conventional foams. The invention further relates to a method of producing such a porous body ( 10, 20 ) and to an apparatus comprising said body ( 10, 20 ) for supporting and/or bearing a person.

The present invention relates to a porous body comprising athree-dimensional network of node points connected to one another bystruts and a void volume present between the struts, which can be usedin the form of a supporting element or bearing element. The inventionalso relates to a method of producing such a porous body and to anapparatus comprising said body for supporting and/or bearing a person.

Supporting elements or bearing elements of the type in question may takethe form, for example, of mattresses. Mattresses of this kind typicallyconsist of foam materials, and the mattresses may especially consist ofmultiple superposed foam layers. In order to increase the lying comfortof such mattresses, it is customary to undertake what is called zoningin mattresses. Zoning of this kind forms zones with different elasticproperties, i.e. different degrees of yielding, distributed over thearea of the mattress. This takes account of the fact that a mattressshould have a different degree of yielding in the leg region, forexample, than in the back region. Formation of zoning of this kind inmultilayer mattresses is typically accomplished by incorporatingcavities in a localized manner into a middle mattress layer withoscillating blades. On the upper and lower sides of this middle mattresslayer, fully continuous upper and lower mattress layers are then appliedin each case.

DE 10 2015 100 816 B3 discloses a process for producing abody-supporting element formed by a mattress, a cushion, a seat or partof a seat, comprising the process steps of defining print data whichform a person-specific three-dimensional support structure and theproduction of the body-supporting element using the print data by meansof a 3D printer. With the print data, it is possible to produce regionsof different elasticity through the formation of cavities of differentsizes and/or different number by means of the 3D printer.

It is stated that, in the process according to DE 10 2015 100 816 B3,production of the body-supporting element can be accomplished usingelastic materials which, in the printing process conducted with the 3Dprinter, are mixed with a binder. Elastic materials used may beelastomeric materials, especially plastics. The 3D printer may havespraying means, in which case elastic materials are sprayed from firstspraying means and binder from second spraying means. The elasticmaterials may be in powder form.

DE 10 2015 100 816 B3 does not make any statements as to whether theelastomeric material forms a porous body. It is stated that, by means ofthe 3D printer, depending on the print data, regions of differentelasticity of the body-supporting element are generated through theformation of cavities of different sizes and/or different number. Inorder to obtain a three-dimensional variation of the elasticity of themattress 3, it is possible to incorporate cavities in a controlledmanner at particular sites in the mattress in the 3D printer. A voidvolume at a particular site is generated by not spraying any binder viathe second spraying means, such that the elastomeric material sprayedvia the first spraying means cannot bond there with the binder to form amaterial structure. Alternatively, it is also possible for noelastomeric material to be sprayed via the first spraying means, suchthat there is no wastage of pulverulent elastomeric material.

DE 10 2015 100 816 B3 states that the cavities generated with the 3Dprinter can have any desired geometries, and these may especially takethe form of inclusions that may be surrounded on all sides by thematerial structure of the mattress. In addition, it is stated that thecavities can be generated in different sizes, and it is especially alsopossible here for very small cavities to be generated, which means thatparticularly high spatial resolution of the variation in the elasticproperties of the mattresses is to be achieved.

Traditionally, flexible polyurethane foams are used in large volumes forthe production of mattresses, cushions and the like, which is documentedin numerous patent and non-patent publications. By contrast, reportsrelating to materials that could be characterized as foams produced byadditive methods are less common.

The publication by Maiti, A. et al. “3D printed cellular solidoutperforms traditional stochastic foam in long-term mechanicalresponse”, Sci. Rep. 6, 24871; doi: 10.1038/srep24871 (2016) describesmaterials formed from polydimethylsiloxane elastomer (PDMS) that areproduced by means of the direct ink writing method. The material wasbuilt up layer by layer, with each layer composed of equally spaced PDMScylinders of diameter 250 μm.

WO 2012/028747 A1 relates to a process for producing a three-dimensionalobject from a construction material by an additive layer constructionmethod, in which, proceeding from material characteristics of theconstruction material and defined properties of the object to bemanufactured, an internal structure of the object comprising a gridstructure is calculated and the three-dimensional object with thisinternal structure is produced by the additive layer constructionmethod, such that it has the defined properties.

An important criterion for the perception of comfort in abody-supporting element, for example a mattress or cushion, is theextent to which the material of the element permits exchange of airthrough the element with the surrounding air. Without this exchange ofair, it would not be possible either for heat to be removed from thehuman body, which leads to increased perspiration, or for moist air fromperspiration from the human body or from a washing process to betransported away.

The problem addressed by the present invention is that of at leastpartly overcoming at least one drawback of the prior art. A furtherproblem addressed by the present invention is that of providing a porousbody suitable for load-bearing for perspiring bodies which permitsoptimized exchange of air (in order to provide maximum comfort for theperspiring body). A further problem addressed by the invention was thatof providing a porous body which, in terms of its perception of comfortfor a user, is comparable to a conventional mattress or cushion. Anadditional problem addressed by the invention was to be able to producea porous body in a very cost-efficient and/or individualized and/orresource-conserving manner.

According to the invention, at least one of these problems is solved bya porous body having the features of claim 1. A production method forsuch a body is provided in claim 13. An apparatus for supporting and/orbearing a person comprising such a body is provided in claim 14.Advantageous developments are specified in the dependent claims. Theycan be combined as desired, unless the opposite is clearly apparent fromthe context.

A porous body according to the invention comprises a three-dimensionalnetwork of node points joined to one another by struts, and a voidvolume present between the struts. The struts have an average length of≥200 μm to ≤50 mm. The struts also have an average thickness of ≥100 μmto ≤5 mm. The porous body has a compression hardness (40% compression,DIN EN ISO 3386-1: 2010-09) in at least one spatial direction of ≥10 to≤100 kPa.

The porous body according to the invention combines the advantages of aconventional mattress or cushion with ventilatability which results fromits porous structure and is not achievable in conventional foams.

The porous body according to the invention can be manufactured in anadditive manufacturing method without external support elements in thevertical construction of its structure.

The struts have an average length of ≥200 μm to ≤50 mm, preferably ≥500μm to ≤10 mm and more preferably ≥750 μm to ≤5 mm. The struts also havean average thickness of ≥100 μm to ≤5 mm, preferably ≥500 μm to ≤2.5 mmand more preferably ≥750 μm to ≤1 mm. If the thickness changes over thecourse of an individual strut, which may quite possibly be intentionalfor construction purposes, the average thickness is first determined forthe individual strut and then this value is used for the calculation ofthe average thickness of the totality of the struts.

A specific example would be a porous body according to the inventionhaving an average length of the struts of ≥4 mm to ≤5 mm and an averagethickness of the struts of ≥800 μm to ≤900 μm.

The porous body according to the invention, also referred to merely asbody hereinafter, can be compressed, in accordance with its end use as asupporting element and/or bearing element. In at least one spatialdirection, the body has a compression hardness (40% compression, DIN ENISO 3386-1:2010-09) of ≥10 to ≤100 kPa, preferably ≥20 to ≤70 kPa andmore preferably ≥30 to ≤40 kPa.

The average spatial density of the node points in the porous bodyaccording to the invention may, for example, be ≥5 node points/cm³ to≤200 node points/cm³, preferably ≥10 node points/cm³ to ≤100 nodepoints/cm³, more preferably ≥30 node points/cm³ to ≤60 node points/cm³.

Suitable materials for the porous body according to the invention areespecially elastomers such as polyurethane elastomers. It is generallythe case that elastomers can be configured as thermoset or thermoplasticmaterials or else mixtures thereof. In the porous body according to theinvention, preference is given to using materials which, at a density of≥1 kg/l, have a Shore A hardness (DIN ISO 7619-1) of ≥40 Shore A and ≤98Shore A, preferably ≥60 Shore A and ≤95 Shore A. Preference is given tothermoplastic polyurethane elastomers.

In a preferred embodiment of the porous body, the porous body has acompression set after 40% compression (DIN ISO 815-1) of ≤5%, preferably≤3%, more preferably ≤1%.

In order to further increase comfort in use as a supporting elementand/or bearing element, the porous body according to the invention mayalso have viscoelastic properties. In a preferred embodiment, the porousbody in at least one spatial direction has a maximum tan δ value (DMA,DIN EN ISO 6721) at ≥−10° C. to ≤40° C., preferably ≥10° C. to ≤35° C.,more preferably ≥18° C. to ≤30° C. Preferably, the porous body has a tanδ value (20° C., DMA, DIN EN ISO 6721) of the body in at least onespatial direction of ≥0.1 to ≤1.5, preferably ≥0.2 to ≤1.2, morepreferably ≥0.3 to ≤1.1.

In a further preferred embodiment of the porous body, the compressionhardness (40% compression, DIN EN ISO 3386-1:2010-09) of the body in aselected spatial direction differs by ≥10%, preferably ≥15% to ≤200%,more preferably ≥20% to ≤100%, from the compression hardness (40%compression, DIN EN ISO 3386-1:2010-09) of the body in a spatialdirection at right angles to the selected spatial direction.

Preferably, the tan δ value (20° C., DMA, DIN EN ISO 6721) of the porousbody in a selected spatial direction differs by ≥10%, or preferably ≥15%to ≤200%, more preferably ≥20% to ≤100%, from the tan δ value (20° C.,DMA, DIN EN ISO 6721) of the body in a spatial direction at right anglesto the selected spatial direction.

A porous body according to the invention with such anisotropiccharacteristics in terms of these mechanical properties is appropriatelyproduced by means of additive manufacturing. In this way, it is possiblein a controlled manner to define the length and thickness of individualstruts, for example, in order to adjust the anisotropic characteristicsof the body.

In a further preferred embodiment, the compression hardness (40%compression, DIN EN ISO 3386-1:2010-09) of the body in a selectedspatial direction differs by ≤10%, preferably ≤5%, more preferably ≤2%,from the compression hardness (40% compression, DIN EN ISO3386-1:2010-09) of the body in other spatial directions.

Additionally or alternatively, the tan δ value (20° C., DMA, DIN EN ISO6721) of the body, preferably in a selected spatial direction, differsby ≤10%, preferably ≤5%, more preferably ≤2%, from the tan δ value (20°C., DMA, DIN EN ISO 6721) of the body in one of the other spatialdirections.

The smaller the difference in the tan δ value of the body in thedifferent spatial directions, the more isotropic the characteristicsthereof in terms of these mechanical properties.

In a further preferred embodiment, the body is formed at least partlyfrom a material having one or more of the following properties:

-   -   a tan δ value (20° C., DMA, DIN EN ISO 6721) of ≥0.1 to ≤1.5,        preferably ≥0.2 to ≤1.2, more preferably ≥0.3 to ≤1.1    -   a maximum tan δ value (DMA, DIN EN ISO 6721) at ≥−10° C. to ≤40°        C., preferably ≥10° C. to ≤35° C., more preferably ≥18° C. to        ≤30° C.    -   a modulus of elasticity (DIN EN ISO 604:2003-12) of ≥1 MPa to        ≤800 MPa, preferably ≥5 MPa to ≤400 MPa, more preferably ≥10 MPa        to ≤200 MPa    -   a Shore hardness (DIN ISO 7619-1:2012-02) of ≥40 A to ≤70 D,        preferably ≥50 Shore A to ≤98 Shore A, more preferably ≥60 Shore        A to ≤95 Shore A    -   a melting point (DIN EN ISO 11357-3:2013-04) of ≤220° C.,        preferably ≥30° C. to ≤210° C., more preferably ≥40° C. to ≤200°        C.    -   a glass transition temperature T_(g) (DMA, DIN EN ISO 6721) of        ≤40° C., preferably ≥−10° C. to ≤40° C., more preferably ≥10° C.        to ≤35° C.

In addition to the embodiments outlined above, properties of the bodymaterial and not of the body per se are thus introduced. It isspecifically an advantage of the body according to the invention thatvariation in the body construction, for example of the body structure,composed of at least one base material can give bodies having differentmechanical properties. This simplifies logistics and stockholding for aproducer. On the other hand, different materials can be processed byadjustment of the body construction to give bodies having comparablemechanical properties, which can mean greater flexibility in theprocurement of starting materials for a producer.

In a further preferred embodiment, the void volume makes up ≥50% to≤99%, preferably ≥55% to ≤95%, more preferably ≥60% to ≤90%, of thevolume of the body. With knowledge of the density of the startingmaterial for the body and a density of the body itself, this parametercan be determined easily. Preferably, the void volume makes up ≥65% to≤85% of the volume of the body.

In a further preferred embodiment, the node points are distributed in aperiodically repeating manner in at least part of the volume of thebody. If the node points are distributed in a periodically repeatingmanner in a volume, this circumstance can be described by the means ofcrystallography. The node points may be arranged in accordance with the14 Bravais lattices: simple cubic (sc), body-centred cubic (bcc),face-centred cubic (fcc), simple tetragonal, body-centred tetragonal,simple orthorhombic, base-centred orthorhombic, body-centredorthorhombic, face-centred orthorhombic, simple hexagonal, rhombohedral,simple monoclinic, base-centred monoclinic and triclinic. Preference isgiven to the cubic lattices sc, fcc and bcc.

The construction of the porous body according to the invention may, atleast in cases of regular arrangement of the node points in the space,also be described as the result of penetration of hollow channelsthrough a formerly solid body. Thus, in a further embodiment, the voidvolume is formed in the form of mutually penetrating first, second andthird groups of channels, wherein a multitude of individual channelswithin each respective group of channels run parallel to one another andthe first group of channels, the second group of channels and the thirdgroup of channels extend in different spatial directions.

For the use of the porous body according to the invention as a cushion,mattress and the like, it may be advantageous when it has regions ofdifferent mechanical properties and especially regions having differentcompression hardness and possibly different tan δ values. Thus, amattress in the region of the shoulder areas may be configured in orderto allow a person lying on his/her side to sink lower than the rest ofthe person's body, in order that the person still lies straight overallwith respect to the spinal column. If the body takes the form of aone-piece mattress, the variation in the mechanical properties canespecially be achieved through one or both of the embodiments describedhereinafter. In this respect, it is possible to achieve a modularconstruction to give a one-piece mattress, a one-piece cushion, etc.

In a further preferred embodiment of the porous body, the averageminimum angle between adjacent struts in the porous body is ≥30° to≤140°, preferably ≥45° to ≤120°, more preferably ≥0° to ≤100°. Thisangle is always ascertained in the unstressed state of the body.Adjacent struts are those struts that have a common node point. Theminimum angle between two adjacent struts should be understood suchthat, considering a strut having multiple adjacent struts that formdifferent angles with the strut in question, the smallest of theseangles is selected. One example of this is a node point having,expressed in chemical language, octahedral coordination. Six strutsemanate from this node point, with opposite struts forming an angle of180° to one another and struts that are directly adjacent in a planeforming an angle of 90° to one another. In this example, the minimumangle between adjacent struts would be 90°.

In a further preferred embodiment of the porous body, the spatialdensity of the node points in a first region of the body is thusdifferent from the spatial density of the node points in a second regionof the body. From a geometric point of view, the centre of the nodepoints is being considered here. The spatial density of the node pointsin the first region of the body may, for example, be ≥5 node points/cm³to ≤200 node points/cm³, preferably ≥10 node points/cm³ to ≤100 nodepoints/cm³, more preferably ≥3 node points/cm³ to ≤60 node points/cm³.The spatial density of the node points in the second region of the bodymay, with the proviso that it is different from the density in the firstregion, for example, be ≥5 node points/cm³ to ≤200 node points/cm³,preferably ≥10 node points/cm³ to ≤100 node points/cm³, more preferably≥3 node points/cm³ to ≤60 node points/cm³.

It is also possible to express the differences in spatial density inthat the spatial density of the node points in a first region of thebody is ≥1.1 times to ≤10 times, preferably ≥1.5 times to ≤7 times, morepreferably ≥2 times to ≤5 times, the spatial density of the node pointsin a second region of the body.

A specific example would be a porous body according to the inventionhaving a density of the node points in a first region of ≥39 nodepoints/cm³ to ≤41 node points/cm³ and a density of the node points in asecond region of ≥19 node points/cm³ to ≤21 node points/cm³.

In a further preferred embodiment of the porous body, the material ofthe body in a first region of the body is different from the material ina second region of the body. Different materials having correspondinglydifferent mechanical properties can preferably be used in a meltlayering process with printheads for more than one material forproduction of the body according to the invention. Useful materials areeither two different materials from one substance class, for example twothermoplastic polyurethane elastomers having different moduli ofelasticity, or two materials from different substance classes. Anexample of this is two members from the group of: thermoplasticelastomers (TPE), thermoplastic polyurethane (TPU), polycarbonate (PC),polyamide (PA), polyethylene terephthalate (PET), polybutyleneterephthalate (PBT), cycloolefinic copolyesters (COC), polyether etherketone (PEEK), polyether amide ketone (PEAK), polyetherimide (PEI),polyimide (PI), polypropylene (PP) or polyethylene (PE),acrylonitrile-butadiene-styrene (ABS), polylactate (PLA),polymethylmethacrylate (PMMA), polystyrene (PS), polyvinyl chloride(PVC), polyoxymethylene (POM), polyacrylonitrile (PAN), polyacrylate orcelluloid.

The present invention further relates to a method of producing a porousbody according to the invention, wherein the body is produced in anadditive manufacturing method. By means of an additive manufacturingmethod, individualized adjustment, for example, of the dampingproperties of a porous body according to the invention that has beenenvisaged as a mattress is possible. “Individualized” means here that itis possible to produce not just individual pieces, but that it is alsopossible to adjust the cushioning properties of a support or bearingelement at different points as desired and as part of the process. It isthus possible, for example, for a mattress to be created individuallyfor a customer according to anatomical requirements or needs. In order,for example, to achieve an optimal pressure distribution when lying onthe mattress, it is first possible to record a pressure profile of thebody on a sensor surface and use the data thus obtained for theindividualization of the mattress. The data are then sent to theadditive manufacturing method in a manner known per se.

The process may be selected, for example, from melt layering (fusedfilament fabrication, FFF, or fused deposition modelling, FDM), inkjetprinting, photopolymer jetting, stereo lithography, selective lasersintering, digital light processing-based additive manufacturing system,continuous liquid interface production, selective laser melting, binderjetting-based additive manufacturing, multijet fusion-based additivemanufacturing, high speed sintering process and laminated objectmodelling. The additive manufacturing method is preferably a sinteringmethod or a melt layering method.

In the context of the present invention, sintering methods are methodswhich utilize thermoplastic powders in particular in order to build uparticles layer by layer. In this context, by means of what is called acoater, thin layers of powder are applied and then selectively melted bymeans of an energy source. The surrounding powder here supports thecomponent geometry. Complex geometries can thus be manufactured in amore economically viable manner than in the FDM method. Moreover,various articles can be arranged or manufactured in tightly packed formin what is called the powder bed. Owing to these advantages,powder-based additive manufacturing methods are among the mosteconomically viable additive manufacturing methods on the market. Theyare therefore used predominantly by industrial users. Examples ofpowder-based additive manufacturing methods are selective lasersintering (SLS) or high-speed sintering (HSS). They differ from oneanother in the method of introducing the energy for the selectivemelting into the plastic. In the laser sintering method, the energy isintroduced via a directed laser beam. In the high-speed sintering (HSS)method, the energy is introduced via infrared (IR) sources incombination with an IR absorber selectively printed into the powder bed.Selective heat sintering (SHS) utilizes the printing unit of aconventional thermal printer in order to selectively melt thermoplasticpowders. Preference is given to selective laser sintering methods (SLS).

The term “melt layering method” refers to a manufacturing method fromthe field of additive manufacturing, with which a workpiece is built uplayer by layer, for example from a fusible plastic. The plastic can beused with or without further additions such as fibres. Machines for FFFare part of the machine class of the 3D printers. This method is basedon the liquefaction of a plastic or wax material in wire form byheating. In the course of final cooling, the material solidifies. Thematerial is applied by extrusion with a heating nozzle which is freelymovable in relation to a plane of manufacture. It is possible hereeither for the manufacturing plane to be fixed and the nozzle to befreely movable or for a nozzle to be fixed and a substrate table (with amanufacturing plane) to be moved, or for both elements, the nozzle andmanufacturing plane, to be movable. The speed with which the substrateand nozzle are movable with respect to one another is preferably withina range from 1 to 200 mm/s. According to the application, the layerthickness is within a range of 0.025 to 1.25 mm; the exit diameter ofthe material jet (nozzle outlet diameter) of the nozzle is typically atleast 0.05 mm.

In the layer-by-layer model production, the individual layers are thuscombined to form a complex part. A body is typically constructed bytracing each working plane line by line (formation of a layer) and thenmoving the working plane upward in the manner of a stack (forming atleast one further layer atop the first layer), giving rise to a shape ina layer-by-layer manner. The exit temperature of the material mixturesfrom the nozzle may, for example, be 80° C. to 420° C. It isadditionally possible to heat the substrate table, for example to 20° C.to 250° C. It is thus possible to prevent excessively fast cooling ofthe layer applied, such that a further layer applied thereon bondssufficiently to the first layer.

The present invention further relates to an apparatus for supportingand/or bearing a person, comprising a porous body according to theinvention. The apparatus according to the invention may, for example, bea bed or a cushioned item of furniture. As well as the porous bodyaccording to the invention that functions as a mattress or cushion area,the apparatus may comprise active and passive elements. Passive elementsare components such as frames, joints, rollers and the like. Activeelements may be actuator motors, for example motors for adjustment of abed geometry, sensors or other elements that provide a desiredfunctionality.

Preferably, the apparatus according to the invention is a bed forhospitals and care institutions. A further preferred field of use isthat of seats in vehicles, especially in vehicles for long distances. Insuch applications, the advantages of the porous body according to theinvention, namely viscoelastic properties coupled with ventilatabilitynot achievable in conventional foams, are manifested particularly well.

In one embodiment, the apparatus according to the invention furthercomprises a ventilator for passing air through at least a portion of theporous body. In the simplest case, air from the environment of theapparatus is guided through at least a portion of the porous body, suchthat the moisture released through perspiration by a person utilizingthe apparatus and sitting or lying on the porous body can be transportedaway easily. This alone increases sitting or lying comfort.

If the air is heated by one or more heating elements with respect toroom temperature (temperature ≥20° C.) or is cooled by one or morecooling elements (temperature ≤20° C.), the perception of comfort can beincreased further.

The present invention is elucidated in detail by the figures whichfollow with reference to preferred embodiments, but without beingrestricted thereto. The figures show:

FIG. 1 a porous body according to the invention in a first view

FIG. 2 the porous body according to the invention from FIG. 1 in anotherview

FIG. 3 the porous body according to the invention from FIG. 1 in anotherview

FIG. 4 a further porous body according to the invention

FIG. 5 a porous structure according to example 1 and 2

FIG. 1 shows a porous body 10 according to the invention in perspectiveview with a three-dimensional network of node points 200 joined to oneanother by struts 100. Between the struts 100 is the void space 300. Atthe edges of the body 10, there are truncated node points 201, thestruts from which project only into the interior of the body 10. FIG. 2shows the same body 10 in a first isometric view and FIG. 3 the samebody 10 in a further isometric view, corresponding to a top view of oneside of the body 10. On the outer faces of the body 10 shown in FIG. 3,there are also truncated node points identified by the reference numeral202.

The node points 200 in the body 10 according to the invention may be inregular distribution in at least part of its volume. It is likewisepossible for them to be in irregular distribution in at least part ofits volume. It is also possible that the body 10 has one or moresub-volumes in which the node points 200 are in regular distribution andone or more sub-volumes in which the node points 200 are in irregulardistribution.

According to the structure of the network composed of struts 100 andnode points 200 in the porous body 10 according to the invention,particular mechanical properties may also be a function of the spatialdirection in which they are determined on the body. This is the case,for example, for the body 10 shown in FIGS. 1 to 3. Along the spatialdirections corresponding to the base factors of the unit cell, thecompression hardness and the tan δ value in particular may be differentthan, for example, in a spatial direction including all three basespectres as components.

It is possible that the void volume 300 makes up ≥50% to ≤99%,preferably ≥55% to ≤95%, more preferably ≥60% to ≤90%, of the volume ofthe body 10. With knowledge of the density of the starting material forthe body and the density of the body itself, it is easily possible todetermine this parameter.

Preferably, the node points 200 in at least part of the volume of thebody 10 are in periodically repeating distribution. When the node points200 in a volume are in periodically repeating distribution, thiscircumstance can be described by the means of crystallography. The nodepoints may be arranged in accordance with the 14 Bravais lattices:simple cubic (sc), body-centred cubic (bcc), face-centred cubic (fcc),simple tetragonal, body-centred tetragonal, simple orthorhombic,base-centred orthorhombic, body-centred orthorhombic, face-centredorthorhombic, simple hexagonal, rhombohedral, simple monoclinic,base-centred monoclinic and triclinic. Preference is given to the cubiclattices sc, fcc and bcc.

Persisting with the crystallographic view, the number of struts 100 viawhich one node point 200 is connected to other node points can beregarded as the coordination number of the node point 200. The averagenumber of struts 100 that proceed from the node points 200 may be ≥4 to≤12, but it is also possible to achieve coordination numbers that areunusual or are impossible in crystallography. For the determination ofthe coordination numbers, truncated node points on the outer face of thebody, as given by reference numeral 201 in FIG. 1, are not taken intoaccount.

The presence of unusual coordination numbers or those that areimpossible in crystallography can especially be achieved when the porousbody according to the invention is produced by means of additivemanufacturing techniques. It is likewise possible that a first group ofnode points 200 has a first average number of struts 100 and a secondgroup of node points has a second average number of struts 100, wherethe first average number is different from the second average number.

In body 10 shown in FIGS. 1 to 3, the node points 200 are arranged in abody-centred cubic lattice. The coordination number and hence theaverage number of struts that proceed therefrom is 8.

It is possible that the average minimum angle between adjacent struts100 is ≥30° to ≤140°, preferably ≥45° to ≤120°, more preferably ≥50° to≤100°. In the case of the body 10 shown in FIGS. 1 to 3, at all points,the minimum angle between the struts 100 is about 70.5° (arccos(⅓)), ascan be inferred from trigonometric considerations relating to the anglebetween the spatial diagonals of a cube.

The structure of the porous body according to the invention may, atleast in cases of regular arrangement of the node points 200 in thespace, also be described as the result of penetration of hollow channelsthrough a formerly solid body 20. Thus, with reference to FIG. 4, thecavity 300 may take the form of mutually penetrating first 310, second320 and third 330 groups of channels, where a multitude of individualchannels 311, 321, 331 within each respective group of channels runparallel to one another and the first group of channels 310, the secondgroup of channels 320 and the third group of channels 330 extend indifferent spatial directions.

The body 20 shown in FIG. 4 has, in its section shown to the left of thefigure, a higher spatial density of node points 200 than in the sectionshown to the right of the figure. For better illustration, theaforementioned embodiment is discussed with reference to the sectionshown on the right. An array 310 of individual channels 311, thedirection of which is specified by arrows, extends through the body atright angles to the face of the body facing toward it. It is of coursenot just the three channels identified by reference numerals but allchannels that extend through the body at right angles to the facespecified.

The same applies to the channels 321 of the group of channels 320 andthe channels 331 of the group of channels 330, which run at right anglesto one another and at right angles to the channels 311 of the firstgroup of channels 310. The material of the body which remains betweenthe mutually penetrating channels 311, 321, 331 forms the struts 100 andnode points 200.

It is possible that the individual channels 311, 321, 331 have apolygonal or round cross section. Examples of polygonal cross sectionsare trigonal, tetragonal, pentagonal and hexagonal cross sections. FIG.4 shows square cross sections of all channels 311, 321, 331. It is alsopossible that the individual channels 311, 321, 331 within the first310, second 320 and third 330 group of channels each have the same crosssection. This is shown in FIG. 4.

It is likewise possible that the cross section of the individualchannels 311 of the first group of channels 310, the cross section ofthe individual channels 321 of the second group of channels 320 and thecross section of the individual channels 331 of the third group ofchannels 330 are different from one another. For example, the channels311 may have a square cross section, the channels 321 a round crosssection, and the channels 331 a hexagonal cross section. The crosssection of the channels determines the shape of the struts 100, and so,in the case of different cross sections, different characteristics ofthe body 20 can also be achieved depending on the spatial directions.

In one variant, the spatial density of the node points 200 in a firstregion of the body 20 may be different from the spatial density of thenode points 200 in a second region of the body 20. This is shown inschematic form in the one-piece body 20 according to FIG. 4. As alreadymentioned, the body 20 shown therein has a higher spatial density ofnode points 20 in its section shown to the left of the figure than inits section shown to the right of the figure. Only every second nodepoint 200 in the left-hand section forms a strut 100 to a node point 200in the right-hand section.

FIG. 5 is described in connection with the Examples as follows in theExperimental part.

EXPERIMENTAL PART Examples

The materials and filaments according to the present invention whichwere used in the following experiments, have been produced by extrusionof the raw materials (in form of granules, pellets, powder or cut incoarse material with a maximum diameter of 4 to 6 mm) at temperaturesbelow 240° C. into filaments with a diameter of 1.75 mm.

The Thermoplastic Polyurethane (TPU) filaments according to the presentinvention with a diameter of 1.75 mm have been produced by extrusion ofa TPU grade based on an aliphatic isocyanate ether/ester-hybrid typewith a hardness of Shore 85 A and a TPU grade based on an aromaticisocyanate ester type with a hardness of Shore 90 A, respectively.

All filaments have been dried prior to use for 24 h at 30° C. in avacuum drying cabinet.

Two porous bodies according to the invention were manufactured using anadditive manufacturing process and their compression hardness wasmeasured.

Example 1

A porous body was manufactured using the additive manufacturing processof fused deposition modelling (FDM). The build material was athermoplastic polyurethane (TPU) filament, made by extrusion of pelletsof a TPU grade based on an aromatic isocyanate ester type with ahardness of Shore 90 A into a round filament with 1.75 mm diameter. Thisfilament was fed into a DD3 extruder mounted on a Prusa 13 printer. Thenozzle temperature of the DD3 extruder was set to 235° C. and the printspeed to 25 mm/s.

The porous body was printed layer-by-layer using the TPU filamentaccording to a section of the scaffold structure as shown in FIG. 5 as acube with an edge length L of 30 mm, a bar width 110 of 2.5 mm and adistance 120 between nodes 200 of the body-centred lattice of 4.5 mm.The section of the scaffold structure was chosen in a manner that allbars end at the faces of the cube in truncated nodes 202 and at theedges of the cube in truncated nodes 201.

The compression hardness of the as manufactured porous body was measuredon the basis of DIN EN ISO 3386-1:2010-09 using an Instron 5566 machinefrom Instron® GmbH, Germany. The measurement was performed at roomtemperature (23° C.) and a traverse speed of 100 min/min. The porousbody was consecutively compressed 3 times by 40% (corresponding to aresidual height L0 of 60% =1.8 cm compared to height L of 3 cm of theuncompressed cube) and relaxed immediately using the same traversespeed. Afterwards, the porous structure was compressed for a fourth timeby 40% and the used force for this compression is recorded. The value isgiven in Table 1.

Example 2

A porous body as of example 1 was manufactured, however, using afilament made out of a TPU grade based on an aliphatic isocyanateether/ester-hybrid type with a hardness of Shore 85 A. The printersettings are equal to the ones given in example 1 and the compressionhardness measurement was performed as described in example 1.

TABLE 1 compression strength investigation based on DIN EN ISO 3386-1:2010-09 TPU grade TPU grade of Ex. 1, of Ex. 2, Material Shore A 90Shore A 85 width [mm] 29.8 28.7 length [mm] 28.3 28.2 hight [mm] 28.329.1 area [mm²] 800.9 820.6 volume [mm³] 23866.5 23551.8 weight [g]4.1550 3.7200 density [g/cm³] 0.1741 0.1579 force for 40% 25.3 18.9compression [N] modulus [N/mm²] 0.0316 0.0230 or Mpa modulus [kPa] 31.623.0

It can be clearly observed, that suitable combinations of 3D printedinventive geometry design and materials with a material hardness (ShoreA)≤98 according to the invention in combination with the inventive voiddensity and distribution yield excellent mechanical results andperfectly target a 40% compression, DIN EN ISO 3386-1:2010-09 of ≥10 to≤100 kPa.

1. Porous body (10, 20) comprising a three-dimensional network of nodepoints (200) joined to one another by struts (100), and a void volume(300) present between the struts (100), characterized in that the struts(100) have an average length of ≥200 μm to ≤50 mm, the struts (100) havean average thickness of ≥100 μm to ≤5 mm, and in that the body has acompression hardness (40% compression, DIN EN ISO 3386-1: 2010-09) in atleast one spatial direction of ≥10 to ≤100 kPa.
 2. Porous body (10, 20)according to claim 1, wherein the body has a compression set after 40%compression (DIN ISO 815-1) of ≤5%.
 3. Porous body (10, 20) according toclaim 1, wherein the body has a tan δ value (20° C., DMA, DIN EN ISO6721) in at least one spatial direction of ≥0.1 to ≤1.5 and/or the bodyhas a maximum tan δ value (DMA, DIN EN ISO 6721) in at least one spatialdirection at ≥−10° C. to ≤40° C.
 4. Porous body (10, 20) according toclaim 1, wherein the compression hardness (40% compression, DIN EN ISO3386-1:2010-09) of the body in a selected spatial direction differs by≥10% from the compression hardness (40% compression, DIN EN ISO3386-1:2010-09) of the body in a spatial direction at right angles tothe spatial direction selected, and/or the tan δ value (20° C., DMA, DINEN ISO 6721) of the body in a selected spatial direction differs by ≥10%from the tan δ value (20° C., DMA, DIN EN ISO 6721) of the body in aspatial direction at right angles to the spatial direction selected. 5.Porous body (10, 20) according to claim 1, wherein the compressionhardness (40% compression, DIN EN ISO 3386-1:2010-09) of the body in aselected spatial direction differs by ≤10% from the compression hardness(40% compression, DIN EN ISO 3386-1:2010-09) of the body in otherspatial directions and/or the tan δ value (20° C., DMA, DIN EN ISO 6721)of the body in a selected spatial direction differs by ≤10% from the tanδ value (20° C., DMA, DIN EN ISO 6721) of the body in other spatialdirections.
 6. Porous body (10, 20) according to claim 1, wherein thebody is at least partly formed from a material having one or more of thefollowing properties: a tan δ value (20° C., DMA, DIN EN ISO 6721) of≥0.1 to ≤1.5 a maximum tan δ value (DMA, DIN EN ISO 6721) at ≥−10° C. to≤40° C. a modulus of elasticity (DIN EN ISO 604:2003-12) of ≥1 MPa to≤800 MPa a Shore hardness (DIN ISO 7619-1:2012-02) of ≥40 A to ≤70 D amelting point (DIN EN ISO 11357-3:2013-04) of ≤220° C. a glasstransition temperature T_(g) (DMA, DIN EN ISO 6721) of ≤40° C.
 7. Porousbody (10, 20) according to claim 1, wherein the void volume (300) makesup ≥50% to ≤99% of the volume of the body (10, 20).
 8. Porous body (10,20) according to claim 1, wherein the node points (200) are distributedin a periodically repeating manner in at least part of the volume of thebody (10, 20).
 9. Porous body (10, 20) according to claim 1, wherein thevoid volume (300) is formed in the form of mutually penetrating first(310), second (320) and third (330) groups of channels, wherein amultitude of individual channels (311, 321, 331) within each respectivegroup of channels run parallel to one another and the first group ofchannels (310), the second group of channels (320) and the third groupof channels (330) extend in different spatial directions.
 10. Porousbody (10, 20) according to claim 1, wherein the average minimum anglebetween adjacent struts (100) is ≥30° to ≤140°.
 11. Porous body (20)according to claim 1, wherein the spatial density of the node points(200) in a first region of the body (10, 20) is different from thespatial density of the node points (200) in a second region of the body(10, 20).
 12. Porous body (10, 20) according to claim 1, wherein thematerial of the body (10, 20) in a first region of the body (10, 20) isdifferent from the material in a second region of the body (10, 20). 13.Method of producing a porous body (10, 20) according to claim 1,characterized in that the body (10, 20) is produced in an additivemanufacturing method.
 14. Apparatus for supporting and/or bearing aperson, comprising a porous body (10, 20) according to claim
 1. 15.Apparatus according to claim 14, further comprising a ventilator forpassing air through at least a portion of the porous body (10, 20).